Selective-circuit-controlling system



Nov. 27, 1.928. 1,693,325 0. C. TRAVER SELECTIVE CIRCUIT CONTROLLING SYSTBI Filed Nov. 17, 1924 Fig.1. 22 2/ 20 /J /.9

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lmventor 1 Oliver GTraver', blzl M W His Att orn 9Q.

Patented Nov. 27, 1928.

UNITED STATES PATENT OFFICE.

OLIVER C. TBAVER, F SCHENECTADY, NEW YORK, ASSIGNOB TO GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YORK.

SELEcTlvE-CIRcUIT cONTBOLLING SYSTEM.

Application filed November 17, 1924. Serial No. 750,264.

This invention relates to the selective control of electric translating devices and it provides an improved arrangement of thermal responsive circuit controlling devices and circuits for effecting the separate energization of the translating devices.

Although not limited thereto, the invention is particularly adapted to control the lamps of a dual intensity street lighting system wherein the high intensity lamps are lighted during the earlier part of the night and lower intensity lamps are lighted during the re mainder of the night.

In such s stems it has been proposed heretofore to e ect the changeover from the high intensity to the low intensity lamp by means of lamp switching relays located at each of the lighting units which are arranged to be operated upon a momentary de-energization o the power supply lines for the lamps. The various forms of lamps switching relays with which I am familiar have re ulred the use of electromagnets for controllin the switch mechanism, thus leaving something to be desired in the way of a less expensive and more simple lamp switching devlce.

In carrying my invention into effect in the form which I now regard as a preferred form, circuit controlling switch mechanism is controlled by means of a pair of thermal responsive movable elements having different heat storage capacities, such as is fully described and claimed in my divisional application Serial No. 97,726, filed March 26, 1926, the elements being arranged to be heated simultaneously responsively to the current in the circuit controlled by the switch mechanism and arranged so as to operate the switch mechanism responsively to thedifi'erence in the rate of coolingof the elements upon a 'vention are designed to have substantially similiar thermal characteristi 3s ofexpansion while having different heat storage capacities. The thermal element 13 is suitably secured at one end to the stationary support 15 and carries the movable circuit controlling contact 10 at the free end thereof. It will be observed that the circuit controlling contacts 11 and 12 are mounted in fixed spaced relation upon opposite ends of yoke 16, the contact 11 being suitably insulated therefrom, and are .supported in cooperating relation with the contact 10 bythe thermal responsive element 14,'one end of which is suitabl secured to the stationary support 17 an the other end is secured to the yoke 16.

As will be more fully described in connection with the operation of my invention, the

thermal responsive elements 13 and 14 are heated by a common energizing current and cooled by the surrounding air. Since the elements 13 and 14 have substantially similar thermal characteristics, each of the elements will flex substantially the same amount upon a given change of temperature thereof. However, due to the fact that the elements have different heat storage capacities, the rate of change of temperature thereof will vary when they are subjected to a common heating or cooling efi'ect. Thus the element having the lesser heat storage capacity will respond to a given heating and cooling eflfect more rapidly than the element having the greater heat storage capacity and a resulting relative movement occurs between the contact members which is dependent upon.

by properly proportioning the relative mass of the supports 15 and 17 with which the respective elements are in heat conducting contact as indicated in the drawing or by properly proportioning the mass of the elements themselves.

In the preferred form of thermal responsive switch mechanism illustrated, the thermal responsive elements 13 and 14 are given an initial bias such that when the elements are at the same temperature, the contact 10 is maintained in firm engagement with the contact 12 and are each arranged to flex in the same direction when heated and cooled. The thermal responsive element 13 has a greater heat storage capacity than element 14 and consequently the former responds more slowly to a heating or cooling eiiect than the latter.

As shown in Fig. 1, the thermal responsiveswitch mechanism is connected to selectively control the energization of the electric translating devices 18 and 19 which may be assumed to be respectively the low intensity lamp and the high intensity lamp of a lightin unit employed in a dual intensity street lig liting system. In accordance with the usual practice, the lamps 18 and 19 are connected in series in a supply line or energizing circuit 20 and the switch 21 is located at the power house or other convenient place in order to control the connection of the supply line 20 to a suitable source of power 22.

In order to separately control the energization of the lamps 18 and 19, the thermal responsive switch mechanism is connected by suitable conductors as shown to establish a short circuit around the lamp 18 when the movable circuit controlling contact 10 is in engagement with the contact 12 and to similarly short circuit the lamp 19 when the con- 7 tact 10 is in engagement with the contact 11.

As thus constructed and arranged the operation 0t my improved form of thermal responsive switch mechanism and control system employing the same is as follows. 7

Upon the operation of switch 21 from the open position to the closed position, the supplyline 20 is energized from the source of supply 22 and since the low candle power lamp 18 is short circuited, current flows from the supply line 20 through the thermal responsive element 14, the cooperating contacts 10 and 12, the thermal responsive element 13 and the high intensity lamp 19, thereby lighting the latter to furnish high intensity illumination. As the current flow continues, the thermal responsive elements 13 and 14 are heated and consequently flex in unison in the same direction and carry the cooperating circuit controlling contacts 10, 11 and 12 as a unit into the position shown in Fig. 2. Due to the fact that the heat storage capacity of thermal responsive element 14'is less than that of element 13, the temperature of the former will increase more rapidly and .the eleand thus force the contact 12 in firmer engagement with the movable cooperating contact 10. After the thermal responsive elements 13 and 14 finally reach a substantially constant temperature, the contacts 10 and 12 are maintained in engagement due to the initial bias of the thermal elements and the high candle power lamp 19 continues to receive energizing current as shown in Fig. 2.

It will be evident that with my improved form of thermal responsive switch mechanism, a temporary failure of the supply source 22 or a temporary decrease in current in the supply line 20 due to accidental ground or other causes occurring during the operation of the lighting system will not produce a separation of the contacts 10 and 12 unless continued for an appreciable length of time. This is due to the fact that the support 17 as well as the mass of thermal element 14 serve as heat storage masses to prevent too rapid cooling of the element 14.

It now it should be desired to deenergize the high candle power lamp 19 and energize the low candle power lamp 18, the changeover is effected simply by opening the switch 21 for a short interval. This interrupts the heating current for both thermal responsive element 14 and 13 and each thereupon begins to decrease in temperature at a rate dependent upon the heat storage capacity thereof. Since the heat storage capacity of thermal element 14 is relatively low, the temperature of this element will more rapidly decrease and the resulting flexure of the element will carry the circuit controlling contact 12 out of engagement with the contact 10 and operate the circuit controlling contact 11 into engagement therewith. Durin this limited time interval the movement oi: contact 10 by thermal element 13 is relatively small due to the fact that the larger heat storage capacity of thermal responsive element 13 causes the temperature of this element to decrease at a much slower rate. After the engagement of contact 11 with contact 10,the element 13 actively opposes further movement of element 14, thus maintaining the contacts in firm engagement.

The relative positions of the operating parts of the thermal responsive switch mechanism after this-phase of operation are illustrated in Fig. 3. It will be evident that u on the reclosure of switch 21 current will ow through the low intensity lamp 18, the thermal responsive element 13 and the cooperating contacts 10 and 11 and the high intensity lamp 19 will be short circuited. The heating eiiects of the current flowing through element 13 maintains this element flexed with the circuit controlling contact 10 in engagement with contact 11, as long as the low candle power lamp 18 is maintained energized. During this time, no current flows through the ill) thermal element 14 and since the elements are now active in opposition a good electrical contact is secured.

When the low intensity lamp 18 is deenergized by the opening of switch 21, the thermal responsive element 10 is permitted to cool and after a suflicient time interval again will carry the circuit controlling contact 10 into engagement with the cooperating contact 12 as shown in Fig. 1. Thus the electro responsive switch mechanism is returned to its initial position in which the low intensity lamp 18 is short circuited and the thermal responsive elements 13 and 14 are connected in series with the high intensity lamp 19 to be energized simultaneously therewith upon the reclosure of switch 21.

7 From the foregoing it will be obvious that in a lighting system employing a plurality of thermal responsive switches embodying my invention, even though the several switch mechanisms may become unsynchronized due to grounds, accidental interruptions of the supply circuit, or other cause occurring during the operation of the lighting system, nevertheless each of the switch mechanisms will automatically return to corresponding initial position upon the interruption of the supply circuit for a sufficient time interval.

In accordance with the provisions of the patent statutes I have described the rinciple of operation of my invention toget er with the apparatus which I now consider to represent the. best embodiment thereof, but I would have it understood that the apparatus shown is only illustrative and that the invention may be carried out b other means.

What I claim as new and esire to secure by Letters Patent of the United States is z- 1. In combination, a plurality of electric circuits, controlling means therefor including thermal responsive elements having different heat storage capacities and arranged to be heated in accordance with the current flow in at least one of the circuits and translating devices connected in said circuits to be selectively controlled responsively to the difference in rate of change of temperature of said elements upon variation in the heating current thereof.

2. In combination, controlling means for electric circuits including relatively movable thermal responsive elements connected to be electrically heated by the current in at least one of the electric circuits and having dissimilar movements upon the cooling thereof, a pair of translating devices connected in said circuits, and switch mechanism jointly controlled by said thermostatic elements for short circuiting one of said translating devices rior to said dissimilar move-ments thereof and for short circuiting the other translating device after said dissimilar movements thereof."

3. The combination with a pair of electric translating devices, of switch mechanism for separately energizing said devices, means for operating said switch mechanism responsively to a momentary interruption of the energizing circuit of said devices comprising a pair of thermal current responsive elements having substantially similar thermal characteristics of expansion and different heat storage capacities.

4. The combination with a pair of electric translating devices, of switch mechanism operable between two circuit controlling positions for separately energizing said devices, said switch mechanism being biased to one of said positions, a pair of thermal responsive elements having different heat storage capacities and arranged to operate said switch mechanism to the other position responsively to the difference in the rate of change of temperature of said element, and connections controlled by said switch mechanism for energizing both of said elements when said switch mechanism is in the biased position and for sparately energizing the thermal element of greater heat storage capacity when the switch mechanism is in the other osition.

5. The combination wit a pair of electric translating devices connected in series circuit, of switch mechanism operable between two circuit controlling positions for separately establishing a shunt circuit around each of said devices, said switch mechanism being biased to one of said positions, a pair of himetallic thermal current responsive movable elements connected to be heated responsively to the current in the shunt circuit normally established by said switch mechanism and arranged to operate said switch mechanism to the other circuit controlling position upon a momentary interruption of said series circuit, and connections whereby the thermal element of greater heat storage capacity is heated responsively to the current in the other shunt circuit upon the reclosure of said series circuit to maintain said switch mechanism in the said other position against its bias.

6. In combination, a plurality of electric circuits and a plurality of thermal responsive elements having different thermal characteristics and means controlled by said elements to efi'ect a selective control of said circuits depending on the difference in the rate of change of the temperature of the elements.

7. In combination, a plurality of electric circuits and a plurality of relatively movable thermal responsive elements having different thermal characteristics and arranged to be heated in accordance with the current flow in at least one of the circuits, and switch mechanism ointly controlled by said elements for effecting a selective control of said circuits depending on the difference in the rate of change of the temperature of the elements.

8. In combination, a plurality of electric circuits, a plurality of relatively movable responsive elements having different thermal characteristics, a plurality of translating devices controlled thereby, and connections through which said elements effect a selective control of said devices depending on the difference in the rate of change of the temperature of the elements.

In Witness whereof, I have hereunto set my hand this 15th day of November, 1924.

OLIVER C. TRAVER. 

